JP2849145B2 - Heat-sensitive reversible recording material - Google Patents

Description

The present invention relates to a heat-sensitive reversible recording material.

[Related Art] Conventionally, there has been known a heat-sensitive reversible recording medium in which a recording material in which an organic low-molecular substance is mixed with a resin base material is applied on a support to form a recording layer.

In this method, recording is performed using a phenomenon that a recording material becomes transparent and opaque depending on temperature.

As the organic low-molecular substance in such a recording material, there have been conventionally proposed higher fatty acids and derivatives thereof such as esters and acid amides, alkanols, alkanes, and the like.

In JP-A-54-119377 and JP-A-55-154198, the temperature when clarifying after opacity is generally low, and even if the type of fatty acid is examined, it is about 65 to 72 ° C., and the clarifying temperature range is as follows. Two
It is as narrow as 4 ° C and cannot be used in a specific summer environment in Japan. In addition, at least a part of the recording part which is opaque is made transparent, or a transparent image is formed on an opaque recording material. However, there is a problem in the temperature control at the time of the heat treatment, and there are problems in reliability and practicability.

JP-A-63-39378, JP-A-63-130380, JP-A-1-237
No. 88, etc., is a proposal that considers this point, but expands the temperature range of transparency by including specific organic low-molecular substances such as fatty acid esters, ethers, thioethers, and plasticizers, and increases the practicality. Improvements have been made. However, the improvement of the clearing temperature was not yet sufficient, and the phenomenon that the recorded image sometimes changed and disappeared in an environment of 60 to 65 ° C. was recognized, so the clearing temperature range, the clearing temperature, and the contrast between the opaque part and the transparent part were observed. There is a demand for further improved materials such as.

[Problems to be Solved by the Invention] The present invention is to provide a heat-sensitive reversible recording material which is excellent in environmental preservation resistance and solves the above-mentioned inconveniences and disadvantages, and has a margin for recording control by heating. It is intended for.

[Means for Solving the Problems] The present inventors have conducted intensive studies to solve the above problems, and as a result, as a low molecular substance in the recording material,
The inventors have found that it is effective to select a ketone having a higher alkyl group and a semicarbazone derived therefrom, and have reached the present invention.

That is, the present invention is a heat-sensitive reversible recording material comprising a recording material containing a ketone having a higher alkyl group as a low molecular substance or a semicarbazone derived therefrom and a resin.

The ketone of the present invention or a semicarbazone derived therefrom as an organic low-molecular substance is generally advantageous in expanding the temperature range for clarification as compared with conventional fatty acids, and a substance having a high melting point can be obtained.

Further, in the present invention, the use of a combination of two or more kinds of ketones or semicarbazones derived therefrom makes it possible to adjust the increase or enlargement of the clarification temperature range, and to reduce the temperature-dependent opacity reversible phenomenon depending on the application. It is possible to provide a controlled material.

The ketone used in the present invention contains a ketone group and a higher alkyl group as essential constituent groups, and may also contain an unsubstituted or substituted aromatic ring or heterocyclic ring.

The total carbon number of the ketone is 16 or more, preferably
21 or more.

The semicarbazone used in the present invention is derived from the above ketone.

Ketones and semicarbazones used in the present invention include:
For example, the following can be mentioned.

In order to prepare the thermosensitive reversible recording material of the present invention, (1) a solution in which at least one kind of the resin base material and the organic low-molecular substance of the present invention, that is, ketone or its semicarbazone derivative is dissolved, (2) a solution of the resin base material A dispersion in which the above-mentioned organic low-molecular substance is dispersed in the form of fine particles; (3) a melt of the resin base material and the above-mentioned organic low-molecular substance; To form a heat-sensitive layer. As the solvent for forming the heat-sensitive layer,
Various selections can be made depending on the type of the base material and the organic low-molecular substance, for example, tetrahydrofuran, tetrahydropyran,
Examples thereof include dioxane, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, ethanol, toluene, and benzene. In addition, not only when a dispersion is used, but also when a solution or a melt is used, in a heat-sensitive layer obtained, organic low-molecular substances are precipitated as fine particles and exist in a dispersed state.

The resin base material used for the heat-sensitive layer is a material that forms a layer in which organic low-molecular substances are uniformly dispersed and held, and that affects the transparency at the time of maximum transparency. For this reason, the resin base material is preferably a resin having good transparency, mechanical stability, and good film formability. As such a resin, polyvinyl chloride; vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-acrylate copolymer Vinyl chloride copolymers such as polyvinylidene chloride;
Vinylidene chloride-based copolymers such as vinylidene chloride-vinyl chloride copolymer and vinylidene chloride-acrylonitrile copolymer; polyester; polyamide; polyacrylate or polymethacrylate or acrylate-methacrylate copolymer; silicone resin; These may be used alone or as a mixture of two or more.

On the other hand, the organic low-molecular-weight material may be suitably selected according to selected temperature T0～T ₃ of Figure 1. As such an organic low-molecular substance, at least one of the ketones or the derivatives thereof of the present invention is used, or a mixture of two or more kinds is used.

Further, the ratio of the organic low-molecular substance and the resin base material in the heat-sensitive layer is preferably about 2: 1 to 1:16, more preferably 1: 1 to 1: 3 by weight ratio. If the ratio of the base material is less than this, it is difficult to form a film holding the organic low-molecular substance in the base material, and if it is more than this, it is difficult to make the film opaque because the amount of the organic low-molecular substance is small. . Alternatively, also by using a mixture of two or more, the ratio of the mixture may be suitably selected as desired control temperature shown in the temperature T0～T ₃ of Figure 1.

The thickness of the heat-sensitive layer is generally 1 to 30 μm. If it is thicker than this, the degree of heat sensitivity decreases, and if it is less than this, the contrast decreases.

In addition to the components described above, the following additives can be added to the heat-sensitive layer in order to maintain the clearing temperature range upon repeated heating.

Tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate, tricresyl phosphate, butyl oleate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, phthalate, which are generally used as plasticizers Di-n-octyl acid, di-2-ethylhexyl phthalate, diisononyl phthalate, dioctyl decyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, dibutyl adipate, n-hexyl adipate, di-2-adipic acid Ethylhexyl,
Di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, diethylene glycol dibenzoate, triethylene glycol
2-ethyl butyrate, methyl acetyl ricinoleate,
Examples thereof include butyl acetyl ricinoleate, butyl phthalyl butyl glycolate, and tributyl acetyl citrate.

The ratio between the organic low-molecular substance and these additives is preferably about 1: 0.01 to 1: 0.8 by weight.

[Examples] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The parts here are based on weight.

Example 1 3 parts of a vinyl chloride-vinyl acetate copolymer and 1 part of 2-henicosanone were heated and dissolved in 15 parts of tetrahydrofuran, and this solution was applied on a 75 µm-thick polyester film with a wire bar and dried at 135 to 140 ° C. Thus, a recording sheet was obtained by providing a recording layer having a thickness of 15 μm. This sheet is obtained as cloudy and opaque. This sheet was kept in an oven at a temperature of 95 to 120 ° C. for 30 seconds, then taken out and allowed to cool, to obtain a sheet that turned transparent. Then, when a thermal head whose surface was controlled at 135 ° C. was brought into contact with the recording layer portion, a pattern in which the contact portion became cloudy and opaque was obtained. Magbeth densitometer
The reflection density was measured using RD514. The density of the transparent part was 1.73, and the density of the white turbid part was 0.43.

When this sheet was projected by OHP, the cloudy portion was projected black and could be sufficiently viewed as a projected image. Even when this sheet was left in an oven controlled at 60 to 70 ° C, no change in the cloudiness pattern was observed.

The sheet is then placed again in an oven at a temperature of
After holding for 0 second and taking out and allowing to cool, the cloudy pattern disappeared and a transparent sheet was obtained as a whole.

By repeating the above operation 5 times, the same phenomenon could be recognized stably.

Example 2 A cloudy and opaque recording sheet was prepared by dissolving 3 parts of a saturated polyester resin, 0.98 part of 22-tritetracontanone, and 0.1 part of di-n-heptyl phthalate in 17 parts of tetrahydrofuran under heating according to Example 1. Created. 95 this sheet
After being kept in an oven controlled at 30 ° C. ± 3 ° C. for 30 seconds, it was taken out and allowed to cool to obtain a transparent sheet. This sheet was cut into two sheets, one of which was kept in an oven controlled at 135 ± 3 ° C. for 30 seconds, and then allowed to cool to obtain a cloudy and opaque recording sheet.

The reflection density of the two sheets was measured using a Macbeth densitometer RD514. The values were 1.75 for the transparent sheet and 0.47 for the cloudy opaque sheet.

Example 3 Vinyl chloride-vinyl acetate copolymer resin 3 parts, 18-pentatriacontanone 0.95 part, 2-docosanoylnaphthalene
A cloudy and opaque film sheet was obtained according to Example 1 using 0.05 parts and 15 parts of tetrahydrofuran.

This sheet was contact heated from 65 ° C. to 95 ° C. in steps of 5 ° C. using a temperature gradient tester, allowed to cool, and the heated portion was measured with a Magbeth densitometer. At this time, the temperature at which the reflection density exceeded 1.0 was defined as the transparency temperature, and the range was determined.

Example 4 3 parts of a vinyl chloride-vinyl acetate copolymer, 0.8 parts of 2-henicosanone, and 0.2 parts of 2-henicosanone semicarbazone were opaque and opaque according to Example 1 using a 1: 1 vol mixed solvent of tetrahydrofuran / methyl ethyl ketone. Was obtained. This sheet was kept in an oven at 85 to 100 ° C. for 30 seconds, and then allowed to cool to obtain a sheet that turned transparent.

Next, the contact portion is made opaque and opaque by contacting a thermal head heated to 135 ° C. or more with the surface of the transparent sheet, and the reflection density of the opaque opaque portion is measured using a Magbeth densitometer RD514. The opaque part showed 0.38, and a high contrast was obtained.

[Effects of the Invention] As described above, a ketone having a higher alkyl group or a semicarbazone derived therefrom has been found as a low-molecular organic substance. The temperature range can be controlled in a practically sufficient range, and the effect of improving the environmental stability of the recording material is brought about, so that a general-purpose new reversible recording material can be provided.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view for explaining a transparent turbidity phenomenon depending on the temperature of a thermosensitive reversible recording material.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-1363 (JP, A) JP-A-63-39378 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/36

Claims (2)

(57) [Claims] 1. A heat-sensitive reversible recording material comprising a recording material containing a ketone having a higher alkyl group as a low molecular substance and a resin. 2. The heat-sensitive reversible recording material according to claim 1, wherein the low-molecular substance is semicarbazone derived from the ketone.